Detailed Answer

Short answer: To prove expenses paid for a house in a California partition action you should gather contemporaneous, authenticated receipts and invoices, proof of payment (cancelled checks, bank or credit‑card statements, wire confirmations), contractor contracts and change orders, building permits, photos, and any business‑record declarations or custodian testimony that link those documents to the account holder. Organize them into a clear timeline and accounting so the court can determine which payments are reimbursable, which are improvements, and how to adjust sale proceeds or award credits.

Why documentation matters in a partition case

When co‑owners cannot agree, a partition action asks the court to divide or sell the property and distribute proceeds. The court will decide whether one co‑owner who paid for repairs, taxes, mortgage payments, or improvements should be reimbursed from the sale proceeds or given credit. Judges rely on reliable, authenticated documentary evidence and corroborating testimony, not memory alone.

Key categories of paperwork to collect

• Original receipts and invoices: Itemized receipts from suppliers or contractors showing date, description of work or materials, amounts, and payee.
• Proof of payment: Cancelled checks (front and back), cleared check images from bank, bank statements showing the disbursement, credit‑card statements, and wire transfer confirmations. These connect the invoice to an actual payment.
• Bank and credit‑card statements: Monthly statements that show the transaction and the account owner. If you cannot produce originals, obtain certified or authenticated copies from the bank.
• Contracts, change orders, and estimates: Signed contractor agreements, work scopes, and signed change orders which explain why and how repair or improvement work was done.
• Permits and inspection records: City or county permits and final inspection records for work that required permits. These show the work was authorized and completed per code.
• Photos and condition reports: Before/after photos, damage reports, and written estimates help prove necessity and timing.
• Property tax, insurance, and mortgage records: Tax bills and proof of payment, insurance premium invoices and evidence of payment, mortgage statements and proof payments to mortgage lender. These often affect contribution claims.
• HOA/utility invoices and receipts: Outstanding HOA dues, special assessments, and utility bills paid to preserve the property.
• Ledgers and reconciliations: A simple spreadsheet or ledger that lists each payment, date, payee, invoice number, and the documents that prove the payment.
• Third‑party declarations: Declarations (written statements under penalty of perjury) from contractors, property managers, or vendors confirming the work and payment.

How to authenticate documents for court

California courts admit business records through the business‑records exception to the hearsay rule if properly authenticated. A practical way to do this is to obtain a business‑records declaration or testimony from a records custodian who can state how the records were made and maintained. See California Evidence Code § 1271 for the business‑records exception and requirements for admissibility: Cal. Evid. Code § 1271.

For bank records, ask the bank for certified or authenticated copies. If the bank will not cooperate voluntarily, an attorney can help serve a proper subpoena for production. For private receipts, a paid invoice plus a matching cancelled check or credit‑card transaction on a statement is often enough to tie payment to the expense.

What the court looks for

• Contemporaneous records — documents created at or near the time of the expense.
• Clear link between invoice and payment — e.g., invoice matched with cancelled check or statement entry.
• Proof the expense was necessary to preserve the property (emergency repairs) or was agreed to by co‑owners.
• Whether the expense was a repair (often recoverable) or an improvement (may increase sale proceeds rather than be paid back directly).
• Corroborating evidence — photos, permits, contractor declarations, or communications among co‑owners showing knowledge or consent.

Practical steps to prepare your paperwork

1. Collect originals where possible. If originals are unavailable, get certified copies from banks, vendors, or the issuing agency.
2. Create a chronological spreadsheet that cross‑references each item to the supporting documents (receipt #, check #, bank statement page).
3. Label and paginate documents for easy reference in court filings and exhibits.
4. Get contractor/ vendor declarations that confirm services and payments, signed under penalty of perjury.
5. Keep copies of permits, inspection reports, and correspondence with co‑owners about the work.
6. Redact private financial information (account numbers) in copies you file, but retain unredacted originals to show the judge or produce under protective order if requested.
7. If the other side refuses to produce records, use discovery tools (requests for production, subpoenas) — consider consulting an attorney to draft and serve these properly.

Common problems and how to avoid them

• Missing receipts: Try to obtain duplicate receipts or obtain written confirmation from the vendor. Bank statements that show the payee and amount help fill gaps.
• Unclear payee names on statements: Provide vendor invoices that match the statement description or a vendor declaration explaining the mismatch.
• Improvements vs repairs dispute: Provide permits, estimates, and before/after photos to show whether work was required to preserve the property (repairs) or intended to add value (improvements).

When to get a lawyer

If the other co‑owner disputes the amounts, refuses discovery, or the accounting is complex (many payments, multiple loans, disputed improvements), consult a California attorney experienced in partition actions. A lawyer can help authenticate records, subpoena bank records, prepare business‑records declarations, and present the accounting to the court.

Helpful Hints

• Start organizing evidence now — courts favor contemporaneous records.
• Match each receipt to a proof of payment and note the purpose of the expense.
• Get contractor declarations that state scope, dates, and payment amounts.
• Obtain permits where required — they strengthen claims for reimbursements.
• Use a dated, paginated exhibit book for hearings or mediations to help the judge follow the accounting.
• Redact sensitive account numbers in public filings but preserve originals for in‑camera review if necessary.
• If a bank will not provide copies voluntarily, an attorney can obtain them by subpoena.
• Document communications with co‑owners about the work and payments — emails and text messages can corroborate consent or notice.
• When in doubt, get professional help: a real‑estate attorney or forensic accountant can make the accounting clearer and more persuasive to a judge.

Disclaimer: This article explains general California legal principles and practical steps for documenting expenses in a partition action. It is for informational purposes only and is not legal advice. For advice about your specific situation, consult a licensed California attorney.