Locksmith software ranges from full shop systems with parts and van stock to simple payment apps. A mobile locksmith mostly needs three things on the phone: the agreed price in writing, a signed ownership record and a way to take the card on the spot.
A lockout service call fee is easiest to collect when it was agreed before you arrived. Text it as a bill, then let the customer pay by Tap to Pay or from the link once they are back inside. After-hours locksmith rates should be stated the same way, so a midnight call never turns into a debate.
A proof of ownership form protects you and the customer. Collect it with a signature on their phone, keep it on their profile, and add a photo of the vehicle or door if you like. Mobile locksmith payments then sit next to the paperwork for that job.
Repeat work is steadier. A rekey invoice for an apartment turnover, commercial locksmith billing for a store's new hardware or a car key replacement payment for a dealership customer can all go out with photos attached, charged to a card the customer authorized or paid from a link. That is what a locksmith invoice app should do for you.