Goods for resale acquired by travelers (sometimes called shuttle trade) are included in general merchandise in the Balance of Payments. In contrast, goods received for personal use by travelers are recorded under travel services. However, goods for own use acquired by travelers in excess of customs thresholds are included in general merchandise. The Balance of Payments Manual 6th Edition (BPM6) states that this treatment is consistent with international merchandise trade statistics. Still, that care needs to be taken to avoid double-counting such goods by including them also under travel (see BPM6 para.10.19-10.20).

In practice, if the total values of goods acquired by travelers over multiple trips are significantly above customs thresholds, the compiler may wish to treat those goods as merchandise rather than travel under such circumstances. And that the size of the phenomenon should be estimated/verified with border surveys and/or studies by customs.

Link to BPM6: https://www.imf.org/external/pubs/ft/bop/2007/pdf/bpm6.pdf