Other deductible travel expenses also include various smaller and larger expenses incurred during off-site work. These expenses can be deducted in the proven amount. If proof is not possible, you can also provide credible evidence of the expenses and estimate the amount.
For some additional costs, you may not have received receipts or may not have kept them (e.g. for tips, luggage storage, business phone calls, loss, theft).
In this case, a self-issued receipt can help to provide credible evidence: Note down the type and amount of the expenses, the place and date on a sheet of paper and confirm the details with your signature.